As a heating device of automobile whose power source is an internal combustion engine, a structure, in which air forcibly fed by a blower is heated by a heater core whose source of heat is cooling water (warm water) of the internal combustion engine and in which the air is blown from blowing ports provided toward a vehicle room, is common.
However, as shown in Patent Publication 1 and Patent Publication 2, a heating device for vehicle using an electric heater as a source of heat has come to attract attention with decrease in cooling loss of internal combustion engines and the appearance of hybrid vehicles and electric cars in recent years. In the device described in Patent Publication 1, a PTC heater is arranged within a foot duct to lead a warm air underfoot. Moreover, in the device described in Patent Publication 2, a PCT heater is arranged in a passage in an instrument panel to lead a warm air to driver's knees.
In the heating device for vehicle using an electric heater, it is important how to efficiently conduct heating with a limited electric power.
In the device described in Patent Publication 1, a PTC heater which laminates a lot of structures each putting a tabular PTC ceramic between fins which are made of metal plates is used. As this is a structure that the PTC ceramic heats the fins and thereby these fins warm up air, electric power is uselessly consumed in heating the fins. Besides, in such a structure, it is difficult to arrange a heater at a position immediately upstream of a blowing port, so heat tends to be taken by a duct or a surrounding structure.
Furthermore, in the device described in Patent Publication 2, as it is a structure that a whole space in an instrument panel is warmed by a PTC heater, heat is consumed by the temperature increase of the instrument panel and the surrounding structure. Therefore, only airflow can't be efficiently heated.